PIV ANALYSIS OF FLOW STRUCTURES AROUND SKEWED SPUR DIKES

Spur dikes become to be recognized as hydraulic structures for environmental functions as well as for bank protection works. To predict and control flow, sediment transport and water quality exchange by using submerged spur-dike, it is necessary to clarify three-dimensional flow structures around spur-dike zones. In this study, orientation angle of super dike is chosen as a design parameter and its effects on flow structures in spur-dike zones are investigated by using PIV method. The vertical vortices caused by the top flow and transverse vortices caused by the side flow interact with each other and produce characteristic three-dimensional vortex structures. The orientation angle changes this interaction mechanism significantly. The flow structures of downstream-oriented spur dike are very different from those of upstream-oriented and normal spur dikes.